(a) Common salt is an important raw material for various chemicals of daily use. State in brief the method of preparation of (i) Sodium hydroxide, and (ii) Sodium hydrogen carbonate from common salt. Write balanced chemical equations of the reactions that occur.

OR

(b) Design an experimental set-up to demonstrate that "Alcohol and glucose contain hydrogen but are not categorised as acids". Also give the reason to justify this fact.

(a)(i) Preparation of Sodium Hydroxide (Chlor-Alkali Process):

When electricity is passed through an aqueous solution of sodium chloride (brine), it decomposes to form sodium hydroxide. Chlorine gas is liberated at the anode and hydrogen gas at the cathode, while sodium hydroxide solution is formed near the cathode. This is called the chlor-alkali process (chlor for chlorine, alkali for sodium hydroxide).

Word equation: Sodium chloride + Water $\xrightarrow{\text{electricity}}$ Sodium hydroxide + Chlorine + Hydrogen

$$2NaCl(aq) + 2H_2O(l) \xrightarrow{\text{electricity}} 2NaOH(aq) + Cl_2(g) + H_2(g)$$

(a)(ii) Preparation of Sodium Hydrogencarbonate (Baking Soda):

Sodium chloride, along with water, carbon dioxide and ammonia, is used to manufacture sodium hydrogencarbonate.

Word equation: Sodium chloride + Water + Carbon dioxide + Ammonia $\rightarrow$ Sodium hydrogencarbonate + Ammonium chloride

$$NaCl + H_2O + CO_2 + NH_3 \rightarrow NaHCO_3 + NH_4Cl$$

OR

(b) Experimental set-up (based on Activity 2.8) to show alcohol and glucose contain hydrogen but are not acids:

Fix two nails on a cork and place the cork in a 100 mL beaker. Connect the nails to the two terminals of a 6-volt battery through a bulb and a switch (a simple electrical circuit with the solution as part of the circuit).

• Pour dilute HCl (or dilute $H_2SO_4$) into the beaker and switch on the current — the bulb glows brightly, showing the acid solution conducts electricity because it contains free $H^+(aq)$ ions.
• Empty the beaker, rinse it, and repeat the experiment separately with a glucose solution and then an alcohol solution — in both cases the bulb does not glow, even though molecular glucose ($C_6H_{12}O_6$) and alcohol ($C_2H_5OH$) both contain hydrogen atoms.

Reason: The glowing of the bulb indicates flow of electric current, which is carried through a solution by ions. Since dilute HCl and $H_2SO_4$ conduct electricity, they must contain ions ($H^+(aq)$ and the corresponding anion) in solution. Glucose and alcohol solutions do not conduct electricity, showing that they do not ionise in water to produce $H^+(aq)$ ions — hydrogen is present in them only in covalently bonded molecular form, not as a dissociable ion. Since acidic character is due specifically to the presence of $H^+(aq)$ ions and not merely to the presence of hydrogen atoms in a compound, alcohol and glucose (though hydrogen-containing) are not classified as acids.